1. Field of Invention
The invention relates to wireless communications, and more specifically to a wireless communication device that is capable of efficiently measuring a secondary radio access technology.
2. Related Art
Wireless communication devices, such as cellular telephones to provide an example, are becoming commonplace in both personal and commercial settings. The wireless communication devices provide users with access to all kinds of information, as well as the ability to communicate with other such devices across large distances. For example, a user can access the internet through an internee browser on the device, download miniature applications (e.g., “apps”) from a digital marketplace, send and receive emails, or make telephone calls using a voice over internet protocol (VoIP). Consequently, wireless communication devices provide users with significant mobility, while allowing them to remain “connected” to communication channels and information.
Wireless communication devices communicate with one or more other wireless communication devices or wireless access points to send and receive data. Typically, a first wireless communication device generates and transmits a radio frequency signal modulated with encoded information. This radio frequency signal is transmitted into a wireless environment and is received by a second wireless communication device. The second wireless communication device demodulates and decodes the received signal to obtain the information. The second wireless communication device may then respond in a similar manner. The wireless communication devices can communicate with each other or with access points using any well-known modulation scheme, including simple amplitude modulation (AM), simple frequency modulation (FM), quadrature amplitude modulation (QAM), phase shift keying (PSK), quadrature phase shift keying (QPSK), and/or orthogonal frequency-division multiplexing (OFDM), as well as any other communication scheme that is now, or will be, known.
During communication with a current base station, wireless communication devices repeatedly measure other base stations and report the measurement results to the current base station. The current base station can determine, from the measurements, whether the wireless communication device should handoff to one of the measured base stations. However, the process of measuring and handing off to other base stations is extremely cumbersome, and wastes significant amounts of communication time (and therefore decreases throughput).
In order to perform measurements, typical wireless communication devices measure all cells within range. However, because many of these cells operate on a different frequency than the current base station, the wireless communication device must retune its receiver for each differently-tuned base station. In addition, once a base station has been selected for handoff, the wireless communication device performs several time-consuming steps, including waiting for a time offset from the new base station, which could take up to 10 ms to arrive. The wireless communication device also must search for its preferred PLMN (Public Land Mobile Network), which is unorganized, and therefore can have significant negative effects on system performance.
Consequently, there is a need for a wireless communication device capable of efficiently measuring and handing off to other base stations from a current base station. Further aspects and advantages of the invention will become apparent from the detailed description that follows.
The invention will now be described with reference to the accompanying drawings. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the reference number.